Although the Mac version isn't yet ready for prime time, it is nonetheless a sophisticated piece of software that developers put a fair amount of effort into implementing. It was designed to use Oracle's Java framework to infect not just Macs, but Linux and Windows machines as well, according to Mac antivirus provider Intego. Once installed, the malware gives attackers complete control over the computer.

“While this is an especially malicious piece of malware, the current Mac OS X implementation is flawed, and the threat is therefore low,” Intego researchers wrote in a blog post published Wednesday. “However, Mac users should be aware that this threat exists, and that it is likely to be operative in the future, so this Koobface Trojan horse may become an issue for Macs.”

For that to happen, attackers will probably have to figure out how to bypass a window OS X prominently displays warning that a self-signed Java applet is requesting access to the computer. Assuming they do, or are able to trick users into clicking “Allow” anyway, they will also need to resolve issues preventing the downloaded files from installing.

Those are high hurdles. But Koobface's considerable success on Windows shows just how gullible many marks are when it comes to scams promising free videos.

Once installed, the downloaded files are stored in an invisible folder and give the infected Mac the ability to run a local webserver or IRC server and to act as an DNS changer.

Intego is calling the malware OSX/Koobface.A, while SecureMac, which also blogged about the attack, calls it trojan.osx.boonana.a. ®